1. Technical Field
The present invention relates to a camera stand head comprising a device for attenuating a tilting movement, and a device for compensating gravity torque occurring during this tilting movement.
Cameras which cannot be hand-held, for example owing to their weight or size or owing to specific requirements of a smooth camera movement, are rested on a camera stand or a camera pedestal. The camera is therefore mounted on a camera stand head so as to be rotatable about a horizontal axis (tilting axis) and a vertical axis (swivel axis) so that the cameraman can follow moving objects with the camera lens. (In the following, only the expression “camera stand” is used; the statements are, however, also valid for camera pedestals). When tilting the camera, i.e. when rotating the camera stand head about its tilting axis, the distance of the centre of gravity of the camera from this tilting axis (height of the centre of gravity) together with the weight of the camera causes a torque about the tilting axis, which is dependent on the tilting angle.
The weight compensation device is supposed to allow a force-free tilting of the camera by compensating this tilting torque. It is thus necessary for the weight compensation to be quickly and easily adaptable to different weights and different heights of the centre of gravity owing to the rapid change of the load torque when putting on different cameras or camera accessories such as teleprompters etc.
Furthermore, the weight compensation is supposed to hold the camera directly in any tilting position without any subsequent movement, and this within a tilting range of at least ±90°, in order to be able to cover the entire spatial field of vision when tilting the camera.
To allow gentle tilting movements, the camera stand head should furthermore comprise an attenuating device which is independent of weight compensation and is preferably also adjustable.
2. Prior Art
Known camera stand heads comprise, for example, a hydraulic attenuator having an adjustable torsional resistance to attenuate the tilting movement, as is described in the German patent specification 24 57 267.
Regarding weight compensation, it is known, for example, to compensate the tilting torque with several disk torsion springs made of rubber and arranged consecutively on the tilting axis. Weight compensation can be adapted here by the connection or disconnection of individual springs. It is furthermore known to compensate the tilting torque by means of series connected pressure or tension springs.
If the centre of gravity of the camera lies exactly vertically over the tilting axis at a tilting angle of 0°, the tilting torque has a sinusoidal characteristic curve. The characteristic curve (torque over angle of rotation) of the known arrangement of disk torsion springs is, however, approximately linear so that although it roughly concurs with the sinusoidal characteristic curve of the tilting torque in a tilting range of 0° to approximately 45°, it does, however, deviate increasingly from this characteristic curve at tilting angles of >45°. The compensation torque is therefore too great at large tilting angles and thus a subsequent reverse movement of the camera occurs in the direction of the compensation position.